Chapter 22: Changing Layer Transparency

Changing Layer Transparency

The Motion Book Tool offers three types of transparency effects: Fade In, Fade Out, and Alpha. These three effects parallel the motion effects Slide In, Slide Out, and Move, but instead of moving layers they change layers’ transparency. Each transparency effect defines a start and end transparency for a layer and then changes transparency from start to end over time according to the progression quality set for the effect. But, as with the motion effects, each transparency effect determines start and end values in different ways.

Transparency

Transparency is a value that ranges from 0% (completely invisible) to 100% (completely opaque). Transparency is also called an object’s “alpha value,” which is how the Alpha effect gets its name.

A layer with an attached transparency effect has three different transparencies to consider:

lIts original transparency, which is specified in the layer box by its Transparency slider/value box. This is the transparency you set when you first create a layer without effects, which is set to 100% by default.

lIts end transparency, which is the layer’s transparency when a transparency effect ends.

lIts start transparency, which is the layer’s transparency when a transparency effect starts. If the layer transparency hasn’t been changed by another effect, the start transparency is the original transparency. If the layer transparency was changed by a previous effect, the start transparency is the end transparency of the previous effect. One exception: the Fade In effect, which always has a start transparency of 0%.

You don’t need to think about these different transparencies for simple uses of the transparency effects. But if you combine effects or set a sequence of Alpha effects, it’s important to know how each effect determines a layer’s start transparency, and what the layer’s end transparency is after each effect executes.

Using Fade In Effects

A Fade In effect reveals an object in place on the canvas. It can be sudden, popping into place, or gradual, sneaking into the reader’s view. It is in essence a preset Alpha effect, and is designed to be a layer’s only transparency effect. If you precede or follow a Fade In with an Alpha or Fade Out effect you may get unpredictable results. If you want a sequence of multiple transparency changes, including fades in and out, it’s best to implement the fades using a series of Alpha effects.

Adding a New Fade In Effect

Add a new Fade In effect just as you do any effect as described in “Adding an Effect to a Page” on page 56. You don’t need to set any effect-specific values during creation. When you’ve finished, a Fade In effect box appears in the effect stack. It has no effect-specific controls.

Start and End Transparencies

Fade In is a simple effect that doesn’t require you to specify a start or end transparency. The start transparency is always set to 0%. The end transparency is the layer’s original transparency.

Most fade ins go from 0% to 100%, a layer’s default transparency setting. If you set the original transparency lower to, for example, 50%, the fade in will go from 0% to 50%.

Layer Invisibility Before the Effect

To ensure that a Fade In effectively reveals its layer without showing the layer prematurely, the Motion Book Tool sets the target layer to be invisible before a Fade In effect, even if the layer has other applied effects before the Fade In. It’s best not to apply any other effects before a Fade In effect because you won’t see those effects.

Standard Effect Controls

You can set a Fade In effect’s name, offset, duration, target frame, and progression as described in “Working With Effect Controls” on page 139. Progression is defined by the Motion pull-down in the effect box.

Set the duration of a Fade In effect to 0 to make a layer pop into place without a fade.

Using Fade Out Effects

A Fade Out effect is the reverse of a Fade In effect: it hides an object in place on the canvas. It can be sudden or gradual. It is in essence a preset Alpha effect, and is designed to be a layer’s only transparency effect. If you precede or follow a Fade Out with an Alpha or Fade In effect you may get unpredictable results. If you want a sequence of multiple transparency changes, including fades in and out, it’s best to implement the fades using a series of Alpha effects.

Adding a New Fade Out Effect

Add a new Fade Out effect just as you do any effect as described in “Adding an Effect to a Page” on page 56. You don’t need to set any effect-specific values during creation. When you’ve finished, a Fade Out effect box appears in the effect stack. It has no effect-specific controls.

Start and End Transparencies

Fade Out is a simple effect that doesn’t require you to specify a start or end transparency. The start transparency is the layer’s original transparency; the end transparency is always 0%.

Most fade outs go from 100% (a layer’s default transparency setting) to 0%. If you set the original transparency lower to, for example, 75%, the fade out will go from 75% to 0%.

Layer Invisibility After the Effect

To ensure that a Fade Out effectively hides its layer after the fade, the Motion Book Tool sets the target layer to be invisible after a Fade Out effect, even if the layer has other applied effects after the Fade Out. It’s best not to apply any other effects after a Fade Out effect because you won’t see those effects.

Standard Effect Controls

You can set a Fade Out effect’s name, offset, duration, target frame, and progression as described in “Working With Effect Controls” on page 139. Progression is defined by the Motion pull-down in the effect box.

Set the duration of a Fade Out effect to 0 to make a layer disappear immediately.

Using Alpha Effects

An Alpha effect is a general-purpose transparency effect that give you more control than the fade effects, which are shortcuts for common transparency changes. An Alpha effect lets you specify both start and end transparencies for a fade, not just one. You can create a sequence of Alpha effects to fade a layer in and out as many times as you see fit.

Adding a New Alpha Effect

Add a new Alpha effect just as you do any effect as described in “Adding an Effect to a Page” on page 56. You don’t need to set any effect-specific values during creation; you set the effect once it’s in place using controls in the effect box.

Figure 3:An Alpha effect box offers standard effect controls and an effect-specific alpha % value that specifies the end transparency for the effect.

Start and End Transparencies

An Alpha effect by itself fades its layer from the layer’s original transparency value to the transparency value specified by the Alpha effect’s Alpha % value in the effect box. The layer’s original transparency is the Alpha effect’s start transparency; the Alpha % value is the effect’s end transparency.

If an Alpha effect is preceded by another Alpha effect, the first effect’s end transparency is the start transparency for the second Alpha effect. The second Alpha effect’s Alpha % value is the effect’s end value.

A single Alpha effect by default does not usually fade a layer at all because its Alpha % value (which sets the effect’s end transparency) is set to 100%, which is usually the same as a layer’s transparency. To set an Alpha effect so that it fades a layer, you must change the effect’s Alpha % value to a transparency value that’s different than the effect’s start transparency.

Standard Effect Controls

You can set an Alpha effect’s name, offset, duration, target frame, and progression as described in “Working With Effect Controls” on page 139. Progression is defined by the Motion pull-down in the effect box.

Set the duration of an Alpha effect to 0 to make a layer’s transparency change immediately instead of fading in or out.